Guide to the Secure Configuration of SUSE Linux Enterprise 15
Rules, Groups, and Values defined within the XCCDF Benchmark
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Disable Accepting Router Advertisements on all IPv6 Interfaces by Default
To set the runtime status of the <code>net.ipv6.conf.default.accept_ra</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_ra=0</pre> To make sure...Rule Medium Severity -
Configure Accepting Default Router in Router Advertisements on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.accept_ra_defrtr</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_ra_defrtr=0</pre...Rule Unknown Severity -
Configure Accepting Prefix Information in Router Advertisements on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.accept_ra_pinfo</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_ra_pinfo=0</pre> ...Rule Unknown Severity -
Configure Accepting Router Preference in Router Advertisements on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.accept_ra_rtr_pref</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_ra_rtr_pref=0<...Rule Unknown Severity -
Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv6 Interfaces
To set the runtime status of the <code>net.ipv6.conf.default.accept_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0</pre...Rule Medium Severity -
Configure Auto Configuration on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.autoconf</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.autoconf=0</pre> To make sure t...Rule Unknown Severity -
Disable Kernel Parameter for IPv6 Forwarding by default
To set the runtime status of the <code>net.ipv6.conf.default.forwarding</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.forwarding=0</pre> To make su...Rule Medium Severity -
Configure Maximum Number of Autoconfigured Addresses on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.max_addresses</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.max_addresses=1</pre> To m...Rule Unknown Severity -
Kernel Parameters Which Affect Networking
Thesysctl
utility is used to set parameters which affect the operation of the Linux kernel. Kernel parameters which affect networking and have security implications are described here.Group -
Network Related Kernel Runtime Parameters for Hosts and Routers
Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against certain types of IPv4 protocol attacks.Group -
net.ipv4.conf.all.accept_redirects
Disable ICMP Redirect AcceptanceValue -
net.ipv4.conf.all.accept_source_route
Trackers could be using source-routed packets to generate traffic that seems to be intra-net, but actually was created outside and has been redirected.Value -
net.ipv4.conf.default.arp_filter
Controls whether the ARP filter is enabled or not. 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not t...Value -
net.ipv4.conf.default.arp_ignore
Control the response modes for ARP queries that resolve local target IP addresses: 0 - (default): reply for any local target IP address, configured on any interface 1 - reply only if the target IP...Value -
net.ipv4.conf.all.log_martians
Disable so you don't Log Spoofed Packets, Source Routed Packets, Redirect PacketsValue -
net.ipv4.conf.all.rp_filter
Enable to enforce sanity checking, also called ingress filtering or egress filtering. The point is to drop a packet if the source and destination IP addresses in the IP header do not make sense whe...Value -
net.ipv4.conf.all.secure_redirects
Enable to prevent hijacking of routing path by only allowing redirects from gateways known in routing table. Disable to refuse acceptance of secure ICMP redirected packets on all interfaces.Value -
net.ipv4.conf.all.shared_media
Controls whether the system can send (router) or accept (host) RFC1620 shared media redirects. <code>shared_media</code> for the interface will be enabled if at least one of conf/{all,interface}/sh...Value -
net.ipv4.conf.default.accept_redirects
Disable ICMP Redirect Acceptance?Value -
net.ipv4.conf.default.secure_redirects
Enable to prevent hijacking of routing path by only allowing redirects from gateways known in routing table. Disable to refuse acceptance of secure ICMP redirected packages by default.Value -
net.ipv4.conf.default.shared_media
Controls whether the system can send(router) or accept(host) RFC1620 shared media redirects. <code>shared_media</code> for the interface will be enabled if at least one of conf/{all,interface}/shar...Value -
net.ipv4.icmp_echo_ignore_broadcasts
Ignore all ICMP ECHO and TIMESTAMP requests sent to it via broadcast/multicastValue -
net.ipv4.icmp_ignore_bogus_error_responses
Enable to prevent unnecessary loggingValue -
net.ipv4.tcp_invalid_ratelimit
Configure the maximal rate for sending duplicate acknowledgments in response to incoming invalid TCP packets.Value -
net.ipv4.tcp_rfc1337
Enable to enable TCP behavior conformant with RFC 1337Value -
net.ipv4.tcp_syncookies
Enable to turn on TCP SYN Cookie ProtectionValue -
Disable Accepting ICMP Redirects for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.accept_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0</pre> To mak...Rule Medium Severity -
Configure ARP filtering for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.arp_filter</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.arp_filter=<xccdf-1.2:sub idref="xccd...Rule Medium Severity -
Configure Response Mode of ARP Requests for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.arp_ignore</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.arp_ignore=<xccdf-1.2:sub idref="xccd...Rule Medium Severity -
Disable TIPC Support
The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communications between nodes in a cluster. To configure the system to prevent the <code>tipc</code> kernel module...Rule Low Severity -
Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.rp_filter</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.rp_filter=1</pre> To make sure that th...Rule Medium Severity -
Disable Kernel Parameter for Accepting Secure ICMP Redirects on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.secure_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0</pre> To mak...Rule Medium Severity -
Configure Sending and Accepting Shared Media Redirects for All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.shared_media</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.shared_media=<xccdf-1.2:sub idref="...Rule Medium Severity -
Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.default.accept_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0</pre...Rule Medium Severity -
Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default
To set the runtime status of the <code>net.ipv4.conf.default.accept_source_route</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=...Rule Medium Severity -
Enable Kernel Paremeter to Log Martian Packets on all IPv4 Interfaces by Default
To set the runtime status of the <code>net.ipv4.conf.default.log_martians</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.log_martians=1</pre> To mak...Rule Unknown Severity -
Verify Permissions on /var/log/messages File
To properly set the permissions of/var/log/messages
, run the command:$ sudo chmod 0640 /var/log/messages
Rule Medium Severity -
Configure Kernel Parameter for Accepting Secure Redirects By Default
To set the runtime status of the <code>net.ipv4.conf.default.secure_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0</pre...Rule Medium Severity -
Configure Sending and Accepting Shared Media Redirects by Default
To set the runtime status of the <code>net.ipv4.conf.default.shared_media</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.shared_media=<xccdf-1.2:sub...Rule Medium Severity -
Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.icmp_echo_ignore_broadcasts</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1</pre> To...Rule Medium Severity -
Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.icmp_ignore_bogus_error_responses</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_response...Rule Unknown Severity -
Set Kernel Parameter to Increase Local Port Range
To set the runtime status of the <code>net.ipv4.ip_local_port_range</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.ip_local_port_range=32768 65535</pre> To make ...Rule Medium Severity -
Enable Kernel Parameter to Use TCP RFC 1337 on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.tcp_rfc1337</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.tcp_rfc1337=1</pre> To make sure that the setting is p...Rule Medium Severity -
Network Parameters for Hosts Only
If the system is not going to be used as a router, then setting certain kernel parameters ensure that the host will not perform routing of network traffic.Group -
Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.send_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0</pre> To make su...Rule Medium Severity -
Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default
To set the runtime status of the <code>net.ipv4.conf.default.send_redirects</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0</pre> To...Rule Medium Severity -
Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.ip_forward</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.ip_forward=0</pre> To make sure that the setting is per...Rule Medium Severity -
nftables
<code>If firewalld or iptables are being used in your environment, please follow the guidance in their respective section and pass-over the guidance in this section.</code><br><br> nftables is a su...Group -
Nftables Base Chain Hooks
The possible hooks which can be used to configure the base chain are: <code>ingress</code> (only in netdev family since Linux kernel 4.2, and inet family since Linux kernel 5.10): sees packets imm...Value -
Nftables Chain Names
The rules in nftables are attached to chains. Unlike in iptables, there are no predefined chains like INPUT, OUTPUT, etc. Instead, to filter packets at a particular processing step, a base chain ...Value
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